PLT-3177 - Fixing ordering for custom themes (#3226)

Fix for bot tag and webhook attachments

Adding theme styling for webhooks

Removing embed styling

Improving margins on compcat view for line breaks

webapp/utils/constants.jsx

@@ -466,16 +466,16 @@ export default {
             id: 'mentionHighlightBg',
             uiName: 'Mention Highlight BG'
         },
-        {
-            group: 'centerChannelElements',
-            id: 'mentionHighlightLink',
-            uiName: 'Mention Highlight Link'
-        },
         {
             group: 'linkAndButtonElements',
             id: 'linkColor',
             uiName: 'Link Color'
         },
+        {
+            group: 'centerChannelElements',
+            id: 'mentionHighlightLink',
+            uiName: 'Mention Highlight Link'
+        },
         {
             group: 'linkAndButtonElements',
             id: 'buttonBg',